Intake silencer for an internal combustion engine

ABSTRACT

An intake silencer for an internal combustion engine disposed on the intake side of a carburetor has an expansion chamber formed by a base board and a cover which are shaped like a pan, and in which there are disposed air horns connected to the carburetor and silencer tubes introducing the external air into the chamber. The base board and silencer tubes are integrally molded with synthetic resin.

I United States Patent 11 1 1111 3,835,956

Kishira Sept. 17, 1974 [54] INTAKE SILENCER FOR AN INTERNAL 2,954,0969/1960 McMullen 181 /35 A COMBUSTION ENGINE 3,293,830 12/1966 McKinlay181/35 A [75] Inventor: Nozumu Kishira, Iwata, Japan [73] Assignee:Yamaha Hatsudoki Kabushiki P i E i -St h n J Tomsky Kaisha, lwata-shi,Japan [22] Filed: May 11, 1973 [21] App]. No.: 359,303

[57] ABSTRACT [30] Foreign Application Priority Data An intake silencerfor an internal combustion engine M 13, 1972 J 47-55724 dy dpdn disposedon the intake side of a carburetor has an ex- 52 us. 01. 181/35 A,181/47 R 1121/57 Pansion Chamber formed by a base board and a Cover 511111.01. ..F(i1n 1/00 which are Shaped like and which there are [58]Field of Search 181 B5 A 36 A 47 R 57 disposed air horns connected tothe carburetor and H silencer tubes introducing the external air intothe chamber. The base board and silencer tubes are inte- [56] ReferencesCited grally molded with synthetic resin.

UNITED STATES PATENTS 2,149,836 3/1939 Brown 181/35 A 9 Claims, 5Drawing Figures I 1 l Q i l 22 I 16" PMENIEDSEPI 11914 SHEEI 1 OF 2gggmmsw 71914 SHEEI 2 (1F 2 FIG. 4

IFIG.5

INTAKE SILENCER FOR AN INTERNAL COMBUSTION ENGINE BACKGROUND OF THEINVENTION This invention relates to an intake silencer and moreparticularly to an intake silencer for a small capacity internalcombustion engine.

In a small capacity internal combustion engine mounted on, for example,a small snow vehicle or cultivator, the intake side of a carburetor isprovided with a device for preventing those portions of such vehicleswhich are located near the engine from being stained by the so-calledblow back of a sucked air-fuelmixture from the engine and also forreducing engine suction noises. However, the conventional type of suchdevice is accompanied with various drawbacks, failing fully to meetusers demand. A typical type among such devices of the prior art capableof fully attaining the desired effect of silencing engine suction noisesand preventing the above-mentioned blow back has the shortcomings thatit is not only of complicated structure resulting in high productioncost, subject to frequent failures, and difficult to handle, but alsohas such a great weight that its fitting applies excess stresses to thecarburetor and its joint with the engine, often leading to the damagethereof.

SUMMARY OF THE INVENTION It is accordingly an object of this inventionto provide an intake silencer of simple construction and small weightfor an internal combustion engine which fully silences engine suctionnoises and prevents stains resulting from the blow back of an air-fuelmixture.

Another object of the invention is to provide an intake silencer which,when fitted to an internal combustion engine, saves itself and thecarburetor from undue stresses caused by the shaking of the engineduring its operation.

Still another object of the invention is to provide an intake silencerwhich facilitates the replacement of an air horn undertaken to changeengine characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view, partly insection, of an intake silencer embodying this invention and fitted to acarburetor;

' FIG. 2 is a cross sectional view along line 22 of FIG. 1;

FIG. 3 is an enlarged cross sectional view of the joint of the fittingplate and base board of the intake silencer;

FIG. 4 is a perspective view of a packing used in the joint of FIG. 3;and

FIG. 5 is an enlarged cross sectional view of the joint of the baseboard and its cover of the intake silencer.

DESCRIPTION OF THE INVENTION There will now be described by reference tothe appended drawings an intake silencer embodying this invention.

Throughout the figures, a referential numeral 11 shows a carburetorconnected at one end to the internal combustion engine (not shown) of,for example, a snow vehicle and at the other end provided with an intakeport 12. Coaxially to said intake port 12 is detachably fitted a flaredair horn or funnel 13 by the later described means. To the flange 11a ofthe carburetor ll constituting the peripheral portion of the intake port12 is attached one side of a rectangular fitting plate 15 made of sheetmetal. Against the opposite side of said fitting plate 15 abuts the rearend of the air horn 13. The flange 11a of the intake port 12, thefitting plate 15 and the air horn 13 are fixed in place by screws 14inserted therethrough from the side of the air horn 13. The fittingplate 15 is bored with two openings 15a corresponding to the intakeports 12 of two carburators 11, said openings enabling the intake ports12 to communicate with the air horns 13.

To the fitting plate 15 is fixed a base board 16 shaped like a shallowpan with a continuous rim 16a and pro vided at the bottom with arectangular through hole or an opening 17 into which the air horns 13are inserted. Said base board 16 is fixed to the fitting plate 15 on theperipheral edge of the through hole 17 by screws 18 and nuts 19. Betweenthe fitting plate 15 and base board 16 is interposed an elastic packing21, for example, a rubber packing shown in FIG. 4. This packing 21consists of a rectangular rim member 21a whose dimensions are largeenough to surround the through hole 17, smaller ring members 21bprovided in the same number as the screws 18 (in this embodiment thereare used six smaller diameter ring members 21b arranged at nearly equalperipheral distance apart) and cylindrical members 210 (similarly six inthis embodiment) which are coaxially inserted into holes 16b so as toconnect the rim member 21a to the smaller ring members 21b. Into thecylindrical members 210 are coaxially fitted collars 20 through whichthe screws 18 project beyond the fitting plate 15 with the projectingportions tightened by nuts 19. As the result, the fitting plate 15 andbase board 16 are connected by the elastic packing 21 in airtight andelastic relationship.

The base board 16 is provided with a large number of the later describedsilencer tubes 22 disposed parallel with the air horns 13 and projectinginto a later described expansion chamber 24 at right angles to said baseboard 16. The base board 16 and silencer tubes 22 are integrally moldedfrom synthetic resin. To the peripheral edge of the rim 16a of the baseboard 16 is detachably fitted a cover 23 shaped like a pot with acontinuous side wall 23a and made of synthetic resin. The base board 16and cover 23 define an expansion chamber 24. Between the inner wall ofthe expansion chamber 24 and the projecting end of each silencer tube 22is allowed a proper space, for example, equal to half or one-third ofthe inner diameter of the silencer tube 22. The air horns 13 alsoproject into the expansion chamber 24 with a considerable space allowed,as apparent from FIG. 1, between the inner wall of the expansion chamber24 and the projecting end of each air horn 13.

The cover 23 is detachably fitted to the base board 16, for example, inthe following manner. In the outer wall of the rim 16a of the base board16 are linearly formed a pair of engagement grooves 31 (FIG. 5). On thatside of the rim 16a of the base board 16 which is disposed opposite tosaid engagement grooves 31 is provided an outwardly extending fixingprojection 25. Into the end face of the projection 25 is forcefullyinserted a metal collar 26, in the inner wall of which there is cut outa female screw. On those parts of the inner wall of the side wall 23a ofthe cover 23' which closely face the aforementioned engagement grooves31 of the base board 16 are formed a pair of engagement projections 28engageable with said grooves 31. On the opposite side of the side wall23a of the cover 23 to said paired engagement projections 28 is providedan outwardly extending projection 29 bored with a hole into which thereis inserted a male screw 30 engageable with the female screw of thecollar 26. Accordingly, the cover 23 can be easily fixed to the baseboard 16 by fitting the engagement projections 28 of the cover 23 intothe engagement grooves 31 of the base board 16, and connecting theprojection 29 of the cover 23 to the fixing projection 25 of the baseboard 16. Thus the peripheral edge of the side wall 23a is detachablyfitted with the peripheral edge of the rim 16a.

There will now be described the operation of the intake silencer of theabove-mentioned arrangement. Where an internal combustion engine isoperated under the condition in which the air horns 13, base board 16made of synthetic resin and cover 23 are set in place as illustrated inFIG. 1, external air is conducted in the directions of the arrowsindicated in FIG. 1 into the expansion chamber 24 through a large numberof silencer tubes 22 molded from synthetic resin integrally with thebase board 16. The air conducted in said chamber 24 is expanded and isintroduced into the carburetor 11 through the air horns 13. Where theblow back takes place in the engine, then a fuel, for example, gasoline,contained in an air-fuel mixture ejects backward from the carburator 11into the expansion chamber 24. However, the fuel is obstructed in thepassage by the cover 23 and attaches itself to the inner walls thereof.In the normal operation of the engine, therefore, said blow backedair-fuel mixture is prevented from discharging outside and forcedbackward into the carburetor 11 by the succeeding influx of externalair. Suction noises occurring in the engine, particularly in thecarburetor 11, are eliminated by resonance and interference taking placein the expansion chamber 24 and silencer tubes 22.

According to the above-mentioned embodiment, the base board 16 andsilencer tubes 22 are integrally molded from synthetic resin. Therefore,this assembly is of simple structure and sufficiently small weight toprevent the other parts of the engine from being subjected to a heavyload and in consequence causes little damage thereto.

For the object of this invention, not only the base board 16, but alsothe cover 23 may be formed of synthetic resin. In this case, it isadvised to mold silencer tubes from synthetic resin integrally with thebase board 16 or cover 23. When not molded with the silencer tubes 22,the base board 16 or cover 23 may consist of a suitable material, forexample, metal or 1. An intake silencer for an internal combustionengine disposed on the side of an intake port of a carburetor,comprising a base board fixed to the peripheral portion of said intakeport of the carburetor; a cover, the peripheral edge of said cover beingdetachably fitted with the peripheral edge of said base board; anexpansion chamber defined by said base board and cover; and a pluralityof silencer tubes fixed to at least one of said base board and cover andhaving openings at each end thereof, the openings at one end beingopenin said expansion chamber, the openings at .theother end being openin the external air, said plurality of silencer tubes and said one ofsaid base board and cover being integrally molded from synthetic resin,whereby the external air conducted into said expansion chamber is suckedin said intake port of the carburetor during the operation of theengine.

2. An intake silencer as claimed in claim 1, wherein said base board isshaped like a shallow pan with a continuous rim along the peripherythereof, said cover is shaped like a pot with a continuous side wall andthe peripheral edge of said side wall of said cover isdetachably fittedalong the whole periphery thereof with the peripheral edge of the rim ofsaid base board by engagement means.

3. An intake silencer according to claim 2, wherein the engagement meanscomprises a groove and projection assembly formed on the mutually facingwalls of the base board and cover which is disposed on one side of theperipheral edge of said base board and coverand a screw provided on theopposite side of said assembly to join the base board and cover.

4. An intake silencer as claimed in claim 3, further comprising atubular air horn replaceably fixed to the peripheral portion of saidintake port of the carburetor coaxially therewith, said air hornprojecting into said expansion chamber.

5. An intake silencer as claimed in claim 1, wherein said plurality ofsilencer tubes are projecting from said one of said base board and coverinto said expansion chamber at right angles to said one of said baseboard and cover.

6. An intake silencer as claimed in claim 2, wherein said plurality ofsilencer tubes are integrally molded with said base board and projectinginto said expansion chamber at right angles to said base board.

7. An intake silencer according to claim 2, further comprising a fittingplate fixed to the peripheral portion of said intake port of thecarburetor, said plate being bored with an opening corresponding to saidintake port of the carburetor, the base board being also bored with anopening closed by said fitting plate, and the base board being apartlyjoined with an elastic packing interposed therebetween.

8. An intake silencer as claimed in claim 7, wherein the edge of saidopening of said base board and the peripheral portion of said fittingplate are spatially screwed together with said elastic packinginterposed therebetween.

9. An intake silencer comprising a fitting plate disposed on that sideof a carburetor body on which there is formed an intakeport, throughwhich an air horn is pressed at one end against the body; screws forjoining together the air horn, fitting plate and carburetor body; a baseboard shaped like a shallow pan, bored with an opening for receiving theair horn and provided with a plurality of silencer tubes molded fromsynthetic resin integrally with said base board; an elastic packinghaving a rim member interposed between the peripheral edge of theopening of the base board and the peripheral edge of the fitting plate;screws for joining together the whole peripheral length thereof aperipheral edge of the pan-shaped base board and defining an expansionchamber with the fitting plate and base board; and means for detachablyfitting the peripheral edge of the the elastic packing, fitting plateand base board; a pot- 5 cover to that of the base board.

shaped cover having a peripheral edge matching along

1. An intake silencer for an internal combustion engine disposed on theside of an intake port of a carburetor, comprising a base board fixed tothe peripheral portion of said intake port of the carburetor; a cover,the peripheral edge of said cover being detachably fitted with theperipheral edge of said base board; an expansion chamber defined by saidbase board and cover; and a plurality of silencer tubes fixed to atleast one of said base board and cover and having openings at each endthereof, the openings at one end being open in said expansion chamber,the openings at the other end being open in the external air, saidplurality of silencer tubes and said one of said base board and coverbeing integrally molded from synthetic resin, whereby the external airconducted into said expansion chamber is sucked in said intake port ofthe carburetor during the operation of the engine.
 2. An intake silenceras claimed in claim 1, wherein said base board is shaped like a shallowpan with a continuous rim along the periphery thereof, said cover isshaped like a pot with a continuous side wall and the peripheral edge ofsaid side wall of said cover is detachably fitted along the wholeperiphery thereof wiTh the peripheral edge of the rim of said base boardby engagement means.
 3. An intake silencer according to claim 2, whereinthe engagement means comprises a groove and projection assembly formedon the mutually facing walls of the base board and cover which isdisposed on one side of the peripheral edge of said base board and coverand a screw provided on the opposite side of said assembly to join thebase board and cover.
 4. An intake silencer as claimed in claim 3,further comprising a tubular air horn replaceably fixed to theperipheral portion of said intake port of the carburetor coaxiallytherewith, said air horn projecting into said expansion chamber.
 5. Anintake silencer as claimed in claim 1, wherein said plurality ofsilencer tubes are projecting from said one of said base board and coverinto said expansion chamber at right angles to said one of said baseboard and cover.
 6. An intake silencer as claimed in claim 2, whereinsaid plurality of silencer tubes are integrally molded with said baseboard and projecting into said expansion chamber at right angles to saidbase board.
 7. An intake silencer according to claim 2, furthercomprising a fitting plate fixed to the peripheral portion of saidintake port of the carburetor, said plate being bored with an openingcorresponding to said intake port of the carburetor, the base boardbeing also bored with an opening closed by said fitting plate, and thebase board being apartly joined with an elastic packing interposedtherebetween.
 8. An intake silencer as claimed in claim 7, wherein theedge of said opening of said base board and the peripheral portion ofsaid fitting plate are spatially screwed together with said elasticpacking interposed therebetween.
 9. An intake silencer comprising afitting plate disposed on that side of a carburetor body on which thereis formed an intake port, through which an air horn is pressed at oneend against the body; screws for joining together the air horn, fittingplate and carburetor body; a base board shaped like a shallow pan, boredwith an opening for receiving the air horn and provided with a pluralityof silencer tubes molded from synthetic resin integrally with said baseboard; an elastic packing having a rim member interposed between theperipheral edge of the opening of the base board and the peripheral edgeof the fitting plate; screws for joining together the elastic packing,fitting plate and base board; a pot-shaped cover having a peripheraledge matching along the whole peripheral length thereof a peripheraledge of the pan-shaped base board and defining an expansion chamber withthe fitting plate and base board; and means for detachably fitting theperipheral edge of the cover to that of the base board.